1. Field of the Invention
The present invention relates to a three-phase alternating-current power supply switching circuit compatible with a plurality of kinds of three-phase alternating-current power supplies.
2. Description of the Background Art
A three-phase alternating-current power supply is used for various technologies. Japanese Patent No. 3900444 discloses a technology as an example in which the three-phase alternating-current power supply is used (hereinafter referred to as a related technology A). Three power conversion parts are used in the related technology A. Moreover, the related technology A controls switching such that the three-phase alternating-current power supply is connected to each power conversion part in a star connection upon a high input voltage and in a delta connection upon a low input voltage. This ensures that each element of a downstream circuit is resistant to a wide range of the input voltages.
Furthermore, a thyristor is used as a switching means that controls switching in the related technology A. The related technology A switches a state of the switching means on the basis of a phase-to-phase voltage (200 V or 400 V) of the three-phase alternating-current power supply.
The three-phase alternating-current power supply includes a plurality of kinds of systems, such as a three-phase three-wire system and a three-phase four-wire system. Thus, a three-phase alternating-current power supply switching circuit compatible with the plurality of kinds of three-phase alternating-current power supplies is required.
In the related technology A, the switching means is used to be compatible with the plurality of kinds of three-phase alternating-current power supplies. However, the thyristor is used as the switching means in the related technology A. Consequently, the related technology A requires a drive circuit for switching the thyristor, a timing control circuit, and a circuit for determining whether or not to control the switching. Therefore, the related technology A has the complex configuration compatible with the plurality of kinds of three-phase alternating-current power supplies.